Self-aligning cutter hub assembly

ABSTRACT

An assembly retainer for a self-aligning pelletizer cutter hub having a self-aligning driving connection between a cutter hub and a drive shaft for the hub in which the cutter hub is capable of universal pivotal movement as well as a driving connection through diametrically located recesses and spherical balls. The retainer is supported on the hub to retain the torque transmitting balls in the recesses. In one embodiment, the balls are retained by circular plates attached to the hub in position to form a closure for an open end of each recess. In another embodiment, spring pins are inserted in passageways in the hub with one end extending into an open end of said recesses to form an obstruction in each recess.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention generally relates to a self-aligning cutterhub assembly mounted on the end of the drive shaft of an underwaterpelletizer which orients the cutter hub and blades mounted thereon inoptimum aligned relation to the die face of the extrusion die plate ofthe underwater pelletizer. More specifically, the present inventionrepresents an improvement on the self-aligning cutter hub structuredisclosed in U.S. Pat. No. 5,624,688 (owned by the Assignee of thepresent application) and includes an assembly retainer in the form ofspring pins or attachments to retain the self-aligning cutter hubelements within the bore of the cutter hub when the underwaterpelletizer is disassembled.

[0003] 2. Description of the Prior Art

[0004] Underwater pelletizers for forming plastic pellets by the use ofan extrusion die having orifices through which molten polymer isextruded out from a die face for engagement by cutter blades mounted ona rotatable cutter hub and driven by a drive shaft are well known. Oneof the characteristics of underwater pelletizers is the desirability ofmaintaining the cutter blades and die face in properly aligned relationin order that the cutting edge of the blades on the rotating cutter hubmove in very close parallel relation to the die face. This closeparallel relationship allows the blades to efficiently cut the extrudedplastic into pellets as the plastic strings are discharged from theorifices in the extrusion die plate and prevents unnecessary wear of thecutter blade and/or die plate face. The following additional U.S.patents, also owned by the Assignee of this application, relate tounderwater pelletizers, cutter hub assemblies and structures forpositioning the cutters and cutter hub in desired relation to the dieface of the die plate: 4,123,207 4,621,996 5,403,176 4,251,198 4,728,2764,500,271 5,059,103

[0005] The above referenced patents, and the references cited in thosepatents, which are incorporated herein as if fully identified, disclosevarious underwater pelletizer structures and components thereof.

[0006] With respect to U.S. Pat. No. 5,624,688 this patent discloses aself-aligning cutter hub assembly which connects the cutter hub to thepelletizer drive shaft. The assembly transmits torque from the driveshaft to the cutter hub while at the same time allowing limiteduniversal movement of the cutter hub in relation to the rotational axisof the drive shaft. This universal movement enables the cutter blades onthe cutter hub to maintain optimum parallel relation to the die face ofthe extrusion die plate to efficiently cut the extruded plastic materialinto pellets. The structure connecting the cutter hub to the drive shaftalso enables effective assembly and disassembly of the components of thecutter hub onto and off of the end of the drive shaft.

[0007] More specifically, the cutter hub of the '688 patent includes acentral bore defining an inner surface and an adapter received in thebore and fixedly attached to the end of the drive shaft. The innersurface of the hub bore and the outer surface of the drive shaft adapterare provided with corresponding partial spherical surfaces which coactto enable the requisite universal movement of the cutter hub in relationto the drive shaft. The drive shaft adapter is mounted on the end of thedrive shaft, as by screw threads or the like, and the adapter and hubbore each include diametrically arranged recesses for partiallyreceiving spherical balls which transmit the driving torque from thedrive shaft to the cutter hub.

[0008] The recesses on the inner surface of the cutter hub bore arepreferably diametrically opposed axial recesses or grooves which extendinwardly from one end surface of the cutter hub but do not extendcompletely to the other end surface of the cutter hub. The inner surfaceof the cutter hub bore also includes a short circumferential recessextending from each edge of the axial recess or groove and opening tothe end surface of the cutter hub open to the axial recess. The recessesenable the adapter and torque transmitting balls to be assembled intothe bore of the cutter hub when the adapter is oriented in perpendicularrelation to the surface of the cutter hub. The drive shaft adapter canthen be rotated 90° to register the partially spherical inner surface inthe bore of the cutter hub with the partial spherical outer surface ofthe adapter.

[0009] The recesses or grooves in the inner surface of the cutter hubbore receive the torque transmitting balls during assembly of the driveshaft adapter with pivoting of the adapter into final position lockingthe torque transmitting balls in position. The adapter can then beassembled onto the drive shaft, such as by a screw threaded engagementbetween the drive shaft and adapter or other engagement assembly.

SUMMARY OF THE INVENTION

[0010] When handling the self-aligning cutter hub assembly as disclosedin the '688 patent, either when assembling for installation in thepelletizer or when disassembling to change or adjust components of thepelletizer, in some instances, the drive shaft adapter can pivot to aposition perpendicular to the cutter hub. In this position, the adaptercan fall out of or disassemble from the hub by gravity if the hub issupported with the open ends of the axial recesses facing downwardly orwhen a force is applied to the adapter that would move the balls out ofthe axial recesses or grooves in the hub. When this occurs, the torquetransmitting balls may fall out of the recesses in the adapter andbecome lost or require considerable time and effort to locate. Thenadditional time is required to reassemble the balls, adapter and cutterhub.

[0011] In order to overcome the foregoing difficulty, the presentinvention provides an assembly retainer for the cutter hub whichincludes a structure that places an obstruction in the open end area ofthe axial recesses. This obstruction then prevents the torquetransmitting balls from moving out of the axial recesses therebymaintaining the hub, drive shaft adapter and balls in assembled relationwhen the self-aligning cutter hub is not assembled on the drive shaftsuch as when components of the cutter hub are being replaced, adjustedand the like.

[0012] In one embodiment, the assembly retainer for the self-aligningcutter hub includes a circular plate or washer associated with the openend of each axial recess in which a torque transmitting ball ispositioned to prevent the ball from exiting the open end of the axialrecess. The ball retaining plates or washers are secured to the cutterhub by the use of a screw threaded fastener or the like extending intothe end surface of the cutter hub to which the axial recess opens,thereby retaining the adapter, balls and cutter hub in assembledrelation and preventing accidental disassembly when the cutter hub isbeing handled, attached to the drive shaft, detached therefrom orotherwise not associated with a die plate or drive shaft.

[0013] In a second embodiment, the assembly retainer for theself-aligning cutter hub includes spring pins inserted in angularpassageways in the cutter hub which communicate with the open end of theaxial recesses in the bore of the cutter hub. A spring pin is insertedin each of the angular passageways with one end of each spring pinterminating in the end of the axial recess and forming an obstruction toprevent the torque transmitting balls from exiting the axial recesses inthe cutter hub and limiting the pivotal movement of the cutter hub inrelation to the adapter during assembly, disassembly and adjustment ofthe cutter hub.

[0014] Preferably, the cutter hub and drive shaft adapter are eachprovided with four recess arrangements oriented at 90° positions aroundtheir circumference. Having four recess arrangements facilitatesmaintenance and enhances the life of the self-aligning cutter hub byenabling an operator of the pelletizer to initially use one set of thediametrically opposed recesses in the outer surface of the adapter, onepair of balls and one set of recesses in the inner surface of the boretogether with appropriate retainers. Then, after requisite use and wear,the pelletizer operator may remove the assembly retainer, disassemblethe adapter and balls from the hub and then reassemble the adapter,balls and hub utilizing the previously unused set of diametricallyopposed recesses in the adapter and hub and inserting the retainers inthe same manner as when oriented in relation to the originally usedrecesses. Optionally, a new set of balls may also be used if theoriginal balls show any evidence of wear. As such, the present inventionenables a prolonged useful life of the self-aligned cutter hub whichwill be retained in assembled relation by the assembly retainers duringhandling, assembly, disassembly and adjustment of the cutter hubassembly.

[0015] Accordingly, it is an object of the present invention to providea self-aligning cutter hub assembly which includes an assembly retainerto keep the torque transmitting balls from coming out of the cutter hubaxial recesses when the components of the cutter hub are being replaced,adjusted and the like.

[0016] Another object of the present invention is to provide aself-aligning cutter hub with an assembly retainer which keeps the driveshaft adapter from inadvertently disassembling from out of the cutterhub bore during handling, assembly, disassembly and adjustment of thecutter hub assembly.

[0017] A further object of the present invention is to provide aself-aligning cutter hub assembly with an assembly retainer which keepsthe cutter hub from coming apart when the hub is handled improperlyduring replacement, adjustment, etc. of the pelletizer components.

[0018] Still another object of the present invention is to provide aself-aligning cutter hub assembly which has a prolonged useful life byreason of a duplicate pair of diametrically opposed recesses in thecutter hub and drive shaft adapter, thus providing duplicate assemblyarrangements.

[0019] These together with other objects and advantages which willbecome subsequently apparent reside in the details of construction andoperation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawings forming a part hereof, whereinlike numerals refer to like parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is a sectional view of a pelletizer illustrating aself-aligning cutter hub associated with other components of apelletizer.

[0021]FIG. 2 is an end elevational view of the cutter hub assembly ofthe present invention without the cutter knives and illustrating theorientation of the components of the hub in a first embodiment of theassembly retainer.

[0022]FIG. 3 is a sectional view, on an enlarged scale, taken alongsection line 3-3 on FIG. 2, illustrating the matching relationshipbetween the exterior of the adapter, the interior of the bore in thecutter hub, the torque transmitting balls and the assembly retainer inthe form of circular plates retaining the balls in the axial recesses inthe hub bore.

[0023]FIG. 4 is an end elevational view of the cutter hub assembly ofthe present invention without the cutter knives and illustrating theorientation of the components of the hub in a second embodiment of theassembly retainer.

[0024]FIG. 5 is a sectional view, on an enlarged scale, taken alongsection line 5-5 on FIG. 4, illustrating the matching relationshipbetween the exterior of the adapter, the interior of the bore in thecutter hub, the torque transmitting balls and the assembly retainer inthe form of spring pins retaining the balls in the axial recesses in thehub bore.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Although only two preferred embodiments of the invention areexplained in detail, it is to be understood that the embodiments aregiven by way of illustration only. It is not intended that the inventionbe limited in its scope to the details of construction and arrangementof components set forth in the following description or illustrated inthe drawings. Also, in describing the preferred embodiments, specificterminology will be resorted to for the sake of clarity. It is to beunderstood that each specific term includes all technical equivalentswhich operate in a similar manner to accomplish a similar purpose.

[0026] Referring now to FIG. 1 of the drawings, this drawing illustratesan underwater pelletizer structure with a self-aligning hub incorporatedtherein as shown in the '688 patent. The pelletizer includes an inlethousing having an inlet passageway 12 for receiving molten polymer fromupstream equipment. The molten polymer is diverted outwardly by a nosecone 14 and enters into a plurality of extrusion orifices 16 in a dieplate 18. The die plate 18 is secured to the inlet housing by fasteningbolts or the like 20 and typically is provided with heating elements 22located in cavities 24 in the die plate. The die plate includes a dieface 26 of wear resistant material which is mounted on the die platealong with heat transfer plates 28.

[0027] Attached to the housing 10 and die plate 18 is a cutter chambergenerally designated by reference numeral 30 which includes acirculating water inlet passageway 32 and a discharge passageway 34 forthe water and entrained pellets. The cutting chamber includes a flange36 attached to the die plate and housing and a flange 38 at the oppositeend thereof having an inclined surface 40 for association with a similarflange on an adapter connected to a drive unit. A drive shaft 42 extendsthrough the cutter chamber 30 and supports and drives a cutter assemblygenerally designated by reference numeral 44. The cutter assembly 44includes a cutter hub 46 and a plurality of cutter knives 48 havingtheir cutting edge associated with the die face 26 and the dischargepoint of the orifices 16. The cutter hub includes two end surfaces, oneend surface 47 faces the die plate 18 and the other end surface 49 facesaway from the die plate toward the drive motor (not shown). All of theabove mentioned structure is known. The present invention relatesspecifically to the cutter hub 46 and the manner in which the componentsthereof are retained in assembled relation.

[0028] As illustrated in FIG. 2, the cutter hub 46 includes a pluralityof arms 50, each having notches 52 which receive the cutter blades thatare secured by the use of conventional fasteners threaded into threadedbores 54 as is well known in the art. The arms 50 are integral with thecentral portion 51 of hub 46. The hub 46 is provided with an axial bore58 which extends therethrough and which has an inner face that ispartially spherical as indicated by reference numeral 60 in FIG. 3.Positioned in the bore 58 is a drive shaft adapter 62 having aninternally threaded bore 64 extending therethrough. The threaded bore 64allows the adapter 62 to be screw threadedly connected onto a reducedexternally threaded end portion 56 of the drive shaft 42 to form a rigidunit. The exterior surface of the adapter 62 is also partially sphericalas indicated by reference numeral 66 in FIG. 3. The curvature of thepartially spherical surfaces 60 and 66 are matching or corresponding andclosely associated as illustrated in FIG. 3. As such, the diameter ofthe partially spherical surfaces at the end edges thereof are less thanthe diameter at the central portions.

[0029] The partially spherical exterior surface 66 of the adapter 62 isprovided with a pair of diametrically opposed generally semisphericalrecesses 68 oriented equally distant from the end edges of the partiallyspherical surface 66 as illustrated in FIG. 3. Received in each of thesemispherical recesses 68 is a spherical ball 70.

[0030] The hub bore 58 includes a pair of diametrically opposed axial,semicylindrical recesses 72 which extend inwardly from end surface 49 ofthe hub bore. The recesses 72 terminate at their inner ends in apartially spherical inner end 74 which is adjacent but spaced from theopposite end surface 47 of the bore 58. The recesses 72 receive theballs 70 which provide the torque transfer from the shaft 42 and adapter62 to the hub 46.

[0031] In order to assemble the adapter 62 and balls 70 with respect tothe bore 58, the bore 58 includes an axial recess 76 in end surface 49which extends circumferentially a short distance from the edges of therecess 72 and terminates with an inner end spaced from the sphericalportion 74 of the recess 72. The recesses 76 are provided to enable thepartially spherical surface 66 of the adapter 62 to be inserted into thebore 58 when the adapter 62 is oriented in substantially perpendicularrelation to the bore. The balls 70 are placed and retained in thecavities 68 in a suitable manner, such as by the application of greaseor the like. With the adapter 62 in substantially perpendicular relationto the hub 46, the balls 70 can be received in the recesses 72 when theassembled adapter 62 is moved into the bore 58. The bore 58 does notblock the larger diameter central portion of the surface 66 of theadapter 62 because of recesses 76 in end surface 49. When the balls 70reach a central point between the two ends of the bore 58, the adapter62 can be rotated 900 into the bore 58 with the partially sphericalsurfaces 60 and 66 being in close registry as illustrated in FIG. 3. Thecurvature of the surfaces 60 and 66 then serves to retain the adapter 62within the bore 58 and retain the balls 70 in the recesses 68 and 72.

[0032] The balls 70 transmit driving torque and the surfaces 60 and 66enable the hub 46 to pivot universally in relation to the drive shaft.This universal movement enables the cutter hub 46 and cutter knives 48to remain oriented in parallel closely spaced relation to the die face26 for efficiently cutting the extruded plastic into pellets regardlessof angular variation in the drive shaft 42.

[0033] After the adapter 62 has been assembled into the cutter hub 46 tothe position illustrated in FIG. 3, the cutter hub and adapter aremounted on the drive shaft 42 by engaging the internal threads 64 of theadapter 62 with the external threads 56 of the drive shaft 42 until theaxial recess 80 formed in one end of the adapter 62 receives theshoulder 82 on the end of the shaft. As assembled, the outer sphericalsurface 66 of the adapter, and the matching inner spherical surface 60of the hub bore 58, are oriented slightly outwardly of the periphery ofthe drive shaft in view of the distance between the periphery of theinternal recess 80 and the periphery of the surfaces 66 and 60 radiallyoutwardly thereof. This assembly enables the cutter hub to pivotuniversally on the end of the drive shaft 42 as defined by the adapter62 which is rigidly secured thereon. While the self-aligning hub hasbeen disclosed in association with a cutter assembly for underwaterpelletizers, it can be adapted for other uses in which a rotatingcomponent is attached to a shaft to enable the rotating component toalign with an associated structure.

[0034] The previously disclosed structure and operational procedure ofthe self-aligning cutter hub correspond with that disclosed in the '688patent. In order to prevent unwanted and accidental disassembly of theadapter 62 from the cutter hub 46 which could occur when the adapter 62and the hub 46 assume a substantially perpendicular relation, such aswhen the cutter hub assembly is separated from the drive shaft, thepresent invention includes an assembly retainer generally designated byreference numeral 90 in FIGS. 2 and 3. The assembly retainer 90 includesa circular flat plate or washer 92 associated with each of the axialrecesses 72 in the cutter hub 46 that is occupied by a ball 70. Theperiphery of the plate or washer 92 forms a closure for the end of therecess 72 thus providing an obstruction to prevent exit of the balls 70from the open end of the recess 72 when the adapter 62 and hub 46 areoriented in a generally perpendicular relation, which occurs by pivotingthe adapter 62 about an axis passing through the opposed balls 70. Inthis position, without the plates or washers 92 being installed, theadapter 62 and the balls 70 can disassemble from the hub 46 as the balls70 move out of the outer ends of the axial recesses 72 in a mannerreverse to the manner of assembling the balls 70 and adapter 62 into thecutter hub 46. The structure of the assembly retainer 90 retains theballs 70 in the axial recesses 72 and prevents unwanted disassembly ofthe balls and adapter from the cutter hub.

[0035] Each of the retainer plates or washers 92 is secured in placepreferably by a screw threaded member 94 extending into and in screwthreaded engagement with a blind bore 96. The bore 96 extends inwardlyinto the cutter hub 46 from end surface 49. The fasteners 94 may beprovided with a screw driver blade receiving kerf or can be providedwith a polygonal periphery for engagement by a wrench or other suitabletool. The retaining plates or washers 92 effectively retain the balls 70in the recesses 72.

[0036] Referring now to FIGS. 4 and 5, a second embodiment of theassembly retainer is illustrated and designated generally by referencenumeral 100. In this embodiment of the invention, the adapter 62 and theballs 70 are the same and their association with the cutter hub alsoremains the same. However, in this embodiment, the cutter hub ismodified and designated by reference numeral 46′. The assembly retainer100 includes a pair of angled passageways 102 formed in the hub 46′ withone end of the passageway 102 communicating with the open end portion ofaxial recess 72′. The other end of the passageway 102 terminates flushwith end surface 47′ of the cutter hub 46′. As illustrated in FIG. 5,each of the recesses 72′ includes a passageway 102 associated therewith.

[0037] Inserted into each passageway 102 is a spring pin 104 whichextends through the passageway 102 and into and through a portion of theopen end of the axial recess 72′. Thus, the end of the spring pin 104which extends into the open end of the axial recess 72′ forms anobstruction to prevent the ball 70 from exiting the axial recess 72′ andfunctions in the same manner as the assembly retainer illustrated inFIGS. 2 and 3. The spring pin 104 is a small tubular sleeve thatincludes a longitudinal slit that can be driven into position andretained in its position by its resiliency. The ends of the spring pin104 are beveled in a manner to be flush with the surfaces 47′ and 49′ ofthe hub 46′ and function to prevent the balls 70 from exiting the axialrecesses 72′ even if the adapter 62 is moved to or assumes perpendicularrelation to the cutter hub 46′.

[0038] In each embodiment of the invention, the drive shaft adapter 62is preferably provided with four semispherical recesses 68 and 68′ andthe cutter hub bore is provided with four axial recesses 72 and 72′ andcorresponding circumferential recesses. This enables an operator of apelletizer to disassemble the components after a predetermined period ofuse and wear and then reassemble the components using the recesses inthe adapter and the cutter hub that were not used during the firstperiod of use. The original balls 70 or new balls can be used dependingupon the wear on the original balls. This enables the operationalcapabilities of the self-aligning hub to extend over a longer period ofuse while maintaining optimum efficiency of the hub and cutters attachedthereto. Thus, for the embodiment shown in FIG. 2, the cutter hub 46 isprovided with fastener receiving bores 96 in 90° spaced relation tothose in use. Likewise, for the embodiment shown in FIG. 4, passageways102 are provided in the cutter hub 46′ in 90° spaced relation to thosewhich are in use to receive a spring pin. This enables maintenance andupkeep to be enhanced without materially increasing the cost ofmanufacturing the cutter hub.

[0039] The foregoing is considered as illustrative only of theprinciples of the invention. Further, since numerous modifications andchanges will readily occur to those skilled in the art, it is notdesired to limit the invention to the exact construction and operationshown and described, and, accordingly, all suitable modifications andequivalents may be resorted to, falling within the scope of theinvention.

What is claimed as new is as follows:
 1. A self-aligning cutter hubassembly for use in an underwater pelletizer connected to a drive shaftand enabling cutter blades on a cutter hub to be aligned with and movein parallel relation to a die face on an extrusion die plate, saidcutter hub assembly comprising a centrally located axial bore defined byan inner surface on said cutter hub, said inner surface of the borebeing partially spherical, an adapter rigidly mountable on an end ofsaid drive shaft and received in said bore, said adapter including apartially spherical outer surface with the partially spherical surfacesbeing closely related and matching each other, each of the partiallyspherical surfaces including a recess receiving a torque transmittingmember partially received in each of the recesses in the matchingsurfaces to drivingly connect the hub to the drive shaft and enablepivotal movement of the hub on said end of said drive shaft, and anassembly retainer on said cutter hub to retain said torque transmittingmember in said recesses.
 2. The cutter hub assembly as defined in claim1, wherein said torque transmitting member is a spherical ball.
 3. Thecutter hub assembly as defined in claim 2, wherein said assemblyretainer is a plate mounted on said hub and forming an obstruction at anouter end of said recess in the hub to retain the ball in the recess. 4.The cutter hub assembly as defined in claim 2, wherein said assemblyretainer includes a spring pin inserted into an angled passageway withone end of the pin extending into the recess in the hub to prevent theball from exiting the recess.
 5. The cutter hub assembly as defined inclaim 1, wherein said partially spherical surface in the cutter hubincludes an axial semicylindrical recess extending from an end surfaceof said cutter hub, said partially spherical surface in the cutter hubincluding recesses extending circumferentially to both sides of thesemicylindrical recess in the cutter hub to enable insertion of thepartially spherical surface of the adapter into cutter hub bore when theadapter is oriented in 90° relation to the cutter hub and inserted intothe cutter hub bore with the semicylindrical recess receiving the torquetransmitting member and the circumferential recesses receiving thepartially spherical surfaces on the adapter to enable assembly of theadapter by moving it inwardly into the bore when in a 90° relation tothe cutter hub and then pivoting it 90° to orient the partiallyspherical surfaces in registry with each other.
 6. In a self-aligningcutter hub for connection with a drive shaft to enable the hub to pivotuniversally in relation to a rotational axis of the drive shaft, saidhub including a bore therethrough having an inner surface provided withan arcuate curvature having a center at the center of the hub, anadapter received in said bore for mounting on a drive shaft, saidadapter having an arcuately curved outer surface having a center at thecenter of the hub to enable relative angular movement of the hub as theedge portions of the adapter move out of alignment with the end surfacesof the hub and torque transmitting members interconnecting the outersurface of the adapter and the inner surface of the hub bore, saidtorque transmitting members being spherical balls partially received inrecesses in each of the curved surfaces and a retainer associated witheach ball receiving recess in said hub bore to retain the balls in therecesses.
 7. The cutter hub as defined in claim 6, wherein the externalsurface of the adapter includes a pair of semispherical recesses, theinternal surface of the bore including axial recesses receiving thetorque transmitting balls and enabling insertion of the exterior surfaceof the adapter into the interior surface of the bore when the adapter isat 90° to the bore with the adapter being rotated 90° to be receivedwithin the bore with the matching curved surfaces and the torquetransmitting balls retaining the adapter in the bore after assembly,said retainer including an obstruction in an end portion of each recessin the internal surface of the bore to prevent the balls from exitingthe recesses in the bore.
 8. The cutter hub as defined in claim 7,wherein said obstruction comprises a retainer member secured in closingrelation to an open end of said recesses in the interior surface of saidhub bore to retain said balls in said recesses.
 9. The cutter hub asdefined in claim 8, wherein said retainer member is a circular plate issecured in place by a screw threaded fastener threaded into said hub.10. The cutter hub as defined in claim 7, wherein said obstructioncomprises spring pins inserted into angled passageways in said hub, saidpins extending into the open end of said recesses to retain said ballsin said recesses in said hub.
 11. A self-aligning cutter hub for use inan underwater pelletizer connected to a drive shaft and enabling cutterblades on the cutter hub to be aligned with and move in substantiallyparallel relation to a die face on an extrusion die plate, said cutterhub including a centrally located partially spherical inner surface, anadapter having a partially spherical outer surface engaged with thepartially spherical inner surface on the hub to enable universal pivotalmovement between the hub and adapter, a torque transmitting memberinterconnecting said partially spherical surfaces to transmit torquefrom said adapter to said hub, said adapter secured to a drive shaft fortransmitting torque to said cutter hub and a retainer structureassociated with the partially spherical surfaces to retain said torquetransmitting member in interconnected relation with said partiallyspherical surfaces.
 12. In combination, a self-aligning cutter hub forconnection with a drive shaft to enable the hub to pivot universally inrelation to a rotational axis of the drive shaft, said hub including aninner surface provided with an arcuate curvature, an adapter drivinglyconnected to the drive shaft, said adapter having an arcuately curvedouter surface engaged with said arcuately curved inner surface on thehub to enable pivotal movement of the hub in relation to the adapter,and torque transmitting structure interconnecting the outer surface ofthe adapter and the inner surface of the hub for driving said hub, and aretainer associated with said hub and adapter to retain said torquetransmitting structure in assembled interconnected relation to the huband adapter.
 13. The hub as defined in claim 12, wherein said torquetransmitting structure includes a pair of projections diametricallyopposed on the arcuately curved outer surface of the adapter, thearcuately curved inner surface of said hub including a pair ofdiametrically opposed recesses aligned with and receiving theprojections on said outer surface of the adapter, each of said recessesin the inner surface of the hub having one end extending to one end ofthe hub to enable insertion of the projections on the adapter when theouter surface of the adapter is engaged with the inner surface of thehub, the recess in the inner surface of the hub an inner end spacedinwardly from the other end of the hub, said recesses in the innersurface of the hub enabling axial insertion of the adapter and torquetransmitting members, said retainer including an obstruction in said oneend of said recesses to retain the torque transmitting members in saidrecesses.
 14. The hub as defined in claim 13, wherein said torquetransmitting members are spherical balls on the curved outer surface ofthe adapter, said recesses in the inner surface of the hub beingsubstantially semicylindrical to enable insertion of said adapter andsaid balls into the recesses in the inner surface of the hub, saidobstruction being in the form of a plate forming a closure for said oneend of each of said recesses in the hub.
 15. The hub as defined in claim13, wherein said torque transmitting members are spherical balls on thecurved outer surface of the adapter, said recesses in the inner surfaceof the hub being substantially semicylindrical to enable insertion ofsaid adapter and said balls into the recesses in the inner surface ofthe hub, said obstruction being in the form of a spring pin insertedinto said one end of each of said recesses in the hub to prevent theball transmitting balls from exiting the recesses in the hub.